The overall goal of the proposed research is to understand the comorbidity between speech sound disorder (SSD) and reading disability (RD). Accomplishing this goal will help us understand the relation between spoken and written language development. Despite their surface differences, it turns out that SSD and RD are co-familial, coheritable, and share a deficit in phonological development. But the comorbidity between SSD and RD is not complete because there are some children with SSD who do not develop RD and some children with RD who never had SSD. Hence, there must also be both etiological and cognitive risk factors that are specific to each disorder, which the proposed research also seeks to identify. We will continue to use molecular methods to specify which genetic risk factors are shared by SSD and RD and which are specific, and we will also examine the contribution of environmental risk and protective factors to these disorders. To increase the power of the molecular analyses, we are recruiting an additional 85 independent sib pairs for a total sample of 150 families and at least 180 sib pairs. To understand which cognitive risk factors are shared by SSD and RD and which are specific, we will complete an ongoing longitudinal study of 111 preschool probands with SSD, and 41 controls similar in age, gender, and SES, adding cross-sectional samples of RD children at both time points: age 5 (before the onset of literacy instruction) and age 8 (early in literacy development). Completing this longitudinal study will allow us to determine how many SSD probands develop RD and to test directly which cognitive deficits are shared by SSD and RD and which are specific at different points in early literacy development.